| // Copyright 2009 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package os provides a platform-independent interface to operating system |
| // functionality. The design is Unix-like, although the error handling is |
| // Go-like; failing calls return values of type error rather than error numbers. |
| // Often, more information is available within the error. For example, |
| // if a call that takes a file name fails, such as Open or Stat, the error |
| // will include the failing file name when printed and will be of type |
| // *PathError, which may be unpacked for more information. |
| // |
| // The os interface is intended to be uniform across all operating systems. |
| // Features not generally available appear in the system-specific package syscall. |
| // |
| // Here is a simple example, opening a file and reading some of it. |
| // |
| // file, err := os.Open("file.go") // For read access. |
| // if err != nil { |
| // log.Fatal(err) |
| // } |
| // |
| // If the open fails, the error string will be self-explanatory, like |
| // |
| // open file.go: no such file or directory |
| // |
| // The file's data can then be read into a slice of bytes. Read and |
| // Write take their byte counts from the length of the argument slice. |
| // |
| // data := make([]byte, 100) |
| // count, err := file.Read(data) |
| // if err != nil { |
| // log.Fatal(err) |
| // } |
| // fmt.Printf("read %d bytes: %q\n", count, data[:count]) |
| // |
| package os |
| |
| import ( |
| "errors" |
| "internal/poll" |
| "internal/testlog" |
| "io" |
| "runtime" |
| "syscall" |
| "time" |
| ) |
| |
| // Name returns the name of the file as presented to Open. |
| func (f *File) Name() string { return f.name } |
| |
| // Stdin, Stdout, and Stderr are open Files pointing to the standard input, |
| // standard output, and standard error file descriptors. |
| // |
| // Note that the Go runtime writes to standard error for panics and crashes; |
| // closing Stderr may cause those messages to go elsewhere, perhaps |
| // to a file opened later. |
| var ( |
| Stdin = NewFile(uintptr(syscall.Stdin), "/dev/stdin") |
| Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout") |
| Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr") |
| ) |
| |
| // Flags to OpenFile wrapping those of the underlying system. Not all |
| // flags may be implemented on a given system. |
| const ( |
| // Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified. |
| O_RDONLY int = syscall.O_RDONLY // open the file read-only. |
| O_WRONLY int = syscall.O_WRONLY // open the file write-only. |
| O_RDWR int = syscall.O_RDWR // open the file read-write. |
| // The remaining values may be or'ed in to control behavior. |
| O_APPEND int = syscall.O_APPEND // append data to the file when writing. |
| O_CREATE int = syscall.O_CREAT // create a new file if none exists. |
| O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist. |
| O_SYNC int = syscall.O_SYNC // open for synchronous I/O. |
| O_TRUNC int = syscall.O_TRUNC // if possible, truncate file when opened. |
| ) |
| |
| // Seek whence values. |
| // |
| // Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd. |
| const ( |
| SEEK_SET int = 0 // seek relative to the origin of the file |
| SEEK_CUR int = 1 // seek relative to the current offset |
| SEEK_END int = 2 // seek relative to the end |
| ) |
| |
| // LinkError records an error during a link or symlink or rename |
| // system call and the paths that caused it. |
| type LinkError struct { |
| Op string |
| Old string |
| New string |
| Err error |
| } |
| |
| func (e *LinkError) Error() string { |
| return e.Op + " " + e.Old + " " + e.New + ": " + e.Err.Error() |
| } |
| |
| // Read reads up to len(b) bytes from the File. |
| // It returns the number of bytes read and any error encountered. |
| // At end of file, Read returns 0, io.EOF. |
| func (f *File) Read(b []byte) (n int, err error) { |
| if err := f.checkValid("read"); err != nil { |
| return 0, err |
| } |
| n, e := f.read(b) |
| return n, f.wrapErr("read", e) |
| } |
| |
| // ReadAt reads len(b) bytes from the File starting at byte offset off. |
| // It returns the number of bytes read and the error, if any. |
| // ReadAt always returns a non-nil error when n < len(b). |
| // At end of file, that error is io.EOF. |
| func (f *File) ReadAt(b []byte, off int64) (n int, err error) { |
| if err := f.checkValid("read"); err != nil { |
| return 0, err |
| } |
| |
| if off < 0 { |
| return 0, &PathError{"readat", f.name, errors.New("negative offset")} |
| } |
| |
| for len(b) > 0 { |
| m, e := f.pread(b, off) |
| if e != nil { |
| err = f.wrapErr("read", e) |
| break |
| } |
| n += m |
| b = b[m:] |
| off += int64(m) |
| } |
| return |
| } |
| |
| // Write writes len(b) bytes to the File. |
| // It returns the number of bytes written and an error, if any. |
| // Write returns a non-nil error when n != len(b). |
| func (f *File) Write(b []byte) (n int, err error) { |
| if err := f.checkValid("write"); err != nil { |
| return 0, err |
| } |
| n, e := f.write(b) |
| if n < 0 { |
| n = 0 |
| } |
| if n != len(b) { |
| err = io.ErrShortWrite |
| } |
| |
| epipecheck(f, e) |
| |
| if e != nil { |
| err = f.wrapErr("write", e) |
| } |
| |
| return n, err |
| } |
| |
| // WriteAt writes len(b) bytes to the File starting at byte offset off. |
| // It returns the number of bytes written and an error, if any. |
| // WriteAt returns a non-nil error when n != len(b). |
| func (f *File) WriteAt(b []byte, off int64) (n int, err error) { |
| if err := f.checkValid("write"); err != nil { |
| return 0, err |
| } |
| |
| if off < 0 { |
| return 0, &PathError{"writeat", f.name, errors.New("negative offset")} |
| } |
| |
| for len(b) > 0 { |
| m, e := f.pwrite(b, off) |
| if e != nil { |
| err = f.wrapErr("write", e) |
| break |
| } |
| n += m |
| b = b[m:] |
| off += int64(m) |
| } |
| return |
| } |
| |
| // Seek sets the offset for the next Read or Write on file to offset, interpreted |
| // according to whence: 0 means relative to the origin of the file, 1 means |
| // relative to the current offset, and 2 means relative to the end. |
| // It returns the new offset and an error, if any. |
| // The behavior of Seek on a file opened with O_APPEND is not specified. |
| func (f *File) Seek(offset int64, whence int) (ret int64, err error) { |
| if err := f.checkValid("seek"); err != nil { |
| return 0, err |
| } |
| r, e := f.seek(offset, whence) |
| if e == nil && f.dirinfo != nil && r != 0 { |
| e = syscall.EISDIR |
| } |
| if e != nil { |
| return 0, f.wrapErr("seek", e) |
| } |
| return r, nil |
| } |
| |
| // WriteString is like Write, but writes the contents of string s rather than |
| // a slice of bytes. |
| func (f *File) WriteString(s string) (n int, err error) { |
| return f.Write([]byte(s)) |
| } |
| |
| // Mkdir creates a new directory with the specified name and permission |
| // bits (before umask). |
| // If there is an error, it will be of type *PathError. |
| func Mkdir(name string, perm FileMode) error { |
| e := syscall.Mkdir(fixLongPath(name), syscallMode(perm)) |
| |
| if e != nil { |
| return &PathError{"mkdir", name, e} |
| } |
| |
| // mkdir(2) itself won't handle the sticky bit on *BSD and Solaris |
| if !supportsCreateWithStickyBit && perm&ModeSticky != 0 { |
| setStickyBit(name) |
| } |
| |
| return nil |
| } |
| |
| // setStickyBit adds ModeSticky to the permision bits of path, non atomic. |
| func setStickyBit(name string) error { |
| fi, err := Stat(name) |
| if err != nil { |
| return err |
| } |
| return Chmod(name, fi.Mode()|ModeSticky) |
| } |
| |
| // Chdir changes the current working directory to the named directory. |
| // If there is an error, it will be of type *PathError. |
| func Chdir(dir string) error { |
| if e := syscall.Chdir(dir); e != nil { |
| testlog.Open(dir) // observe likely non-existent directory |
| return &PathError{"chdir", dir, e} |
| } |
| if log := testlog.Logger(); log != nil { |
| wd, err := Getwd() |
| if err == nil { |
| log.Chdir(wd) |
| } |
| } |
| return nil |
| } |
| |
| // Open opens the named file for reading. If successful, methods on |
| // the returned file can be used for reading; the associated file |
| // descriptor has mode O_RDONLY. |
| // If there is an error, it will be of type *PathError. |
| func Open(name string) (*File, error) { |
| return OpenFile(name, O_RDONLY, 0) |
| } |
| |
| // Create creates the named file with mode 0666 (before umask), truncating |
| // it if it already exists. If successful, methods on the returned |
| // File can be used for I/O; the associated file descriptor has mode |
| // O_RDWR. |
| // If there is an error, it will be of type *PathError. |
| func Create(name string) (*File, error) { |
| return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666) |
| } |
| |
| // OpenFile is the generalized open call; most users will use Open |
| // or Create instead. It opens the named file with specified flag |
| // (O_RDONLY etc.) and perm (before umask), if applicable. If successful, |
| // methods on the returned File can be used for I/O. |
| // If there is an error, it will be of type *PathError. |
| func OpenFile(name string, flag int, perm FileMode) (*File, error) { |
| testlog.Open(name) |
| return openFileNolog(name, flag, perm) |
| } |
| |
| // lstat is overridden in tests. |
| var lstat = Lstat |
| |
| // Rename renames (moves) oldpath to newpath. |
| // If newpath already exists and is not a directory, Rename replaces it. |
| // OS-specific restrictions may apply when oldpath and newpath are in different directories. |
| // If there is an error, it will be of type *LinkError. |
| func Rename(oldpath, newpath string) error { |
| return rename(oldpath, newpath) |
| } |
| |
| // Many functions in package syscall return a count of -1 instead of 0. |
| // Using fixCount(call()) instead of call() corrects the count. |
| func fixCount(n int, err error) (int, error) { |
| if n < 0 { |
| n = 0 |
| } |
| return n, err |
| } |
| |
| // wrapErr wraps an error that occurred during an operation on an open file. |
| // It passes io.EOF through unchanged, otherwise converts |
| // poll.ErrFileClosing to ErrClosed and wraps the error in a PathError. |
| func (f *File) wrapErr(op string, err error) error { |
| if err == nil || err == io.EOF { |
| return err |
| } |
| if err == poll.ErrFileClosing { |
| err = ErrClosed |
| } |
| return &PathError{op, f.name, err} |
| } |
| |
| // TempDir returns the default directory to use for temporary files. |
| // |
| // On Unix systems, it returns $TMPDIR if non-empty, else /tmp. |
| // On Windows, it uses GetTempPath, returning the first non-empty |
| // value from %TMP%, %TEMP%, %USERPROFILE%, or the Windows directory. |
| // On Plan 9, it returns /tmp. |
| // |
| // The directory is neither guaranteed to exist nor have accessible |
| // permissions. |
| func TempDir() string { |
| return tempDir() |
| } |
| |
| // UserCacheDir returns the default root directory to use for user-specific |
| // cached data. Users should create their own application-specific subdirectory |
| // within this one and use that. |
| // |
| // On Unix systems, it returns $XDG_CACHE_HOME as specified by |
| // https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html if |
| // non-empty, else $HOME/.cache. |
| // On Darwin, it returns $HOME/Library/Caches. |
| // On Windows, it returns %LocalAppData%. |
| // On Plan 9, it returns $home/lib/cache. |
| // |
| // If the location cannot be determined (for example, $HOME is not defined), |
| // then it will return an empty string. |
| func UserCacheDir() string { |
| var dir string |
| |
| switch runtime.GOOS { |
| case "windows": |
| dir = Getenv("LocalAppData") |
| |
| case "darwin": |
| dir = Getenv("HOME") |
| if dir == "" { |
| return "" |
| } |
| dir += "/Library/Caches" |
| |
| case "plan9": |
| dir = Getenv("home") |
| if dir == "" { |
| return "" |
| } |
| dir += "/lib/cache" |
| |
| default: // Unix |
| dir = Getenv("XDG_CACHE_HOME") |
| if dir == "" { |
| dir = Getenv("HOME") |
| if dir == "" { |
| return "" |
| } |
| dir += "/.cache" |
| } |
| } |
| |
| return dir |
| } |
| |
| // Chmod changes the mode of the named file to mode. |
| // If the file is a symbolic link, it changes the mode of the link's target. |
| // If there is an error, it will be of type *PathError. |
| // |
| // A different subset of the mode bits are used, depending on the |
| // operating system. |
| // |
| // On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and |
| // ModeSticky are used. |
| // |
| // On Windows, the mode must be non-zero but otherwise only the 0200 |
| // bit (owner writable) of mode is used; it controls whether the |
| // file's read-only attribute is set or cleared. attribute. The other |
| // bits are currently unused. Use mode 0400 for a read-only file and |
| // 0600 for a readable+writable file. |
| // |
| // On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive, |
| // and ModeTemporary are used. |
| func Chmod(name string, mode FileMode) error { return chmod(name, mode) } |
| |
| // Chmod changes the mode of the file to mode. |
| // If there is an error, it will be of type *PathError. |
| func (f *File) Chmod(mode FileMode) error { return f.chmod(mode) } |
| |
| // SetDeadline sets the read and write deadlines for a File. |
| // It is equivalent to calling both SetReadDeadline and SetWriteDeadline. |
| // |
| // Only some kinds of files support setting a deadline. Calls to SetDeadline |
| // for files that do not support deadlines will return ErrNoDeadline. |
| // On most systems ordinary files do not support deadlines, but pipes do. |
| // |
| // A deadline is an absolute time after which I/O operations fail with an |
| // error instead of blocking. The deadline applies to all future and pending |
| // I/O, not just the immediately following call to Read or Write. |
| // After a deadline has been exceeded, the connection can be refreshed |
| // by setting a deadline in the future. |
| // |
| // An error returned after a timeout fails will implement the |
| // Timeout method, and calling the Timeout method will return true. |
| // The PathError and SyscallError types implement the Timeout method. |
| // In general, call IsTimeout to test whether an error indicates a timeout. |
| // |
| // An idle timeout can be implemented by repeatedly extending |
| // the deadline after successful Read or Write calls. |
| // |
| // A zero value for t means I/O operations will not time out. |
| func (f *File) SetDeadline(t time.Time) error { |
| return f.setDeadline(t) |
| } |
| |
| // SetReadDeadline sets the deadline for future Read calls and any |
| // currently-blocked Read call. |
| // A zero value for t means Read will not time out. |
| // Not all files support setting deadlines; see SetDeadline. |
| func (f *File) SetReadDeadline(t time.Time) error { |
| return f.setReadDeadline(t) |
| } |
| |
| // SetWriteDeadline sets the deadline for any future Write calls and any |
| // currently-blocked Write call. |
| // Even if Write times out, it may return n > 0, indicating that |
| // some of the data was successfully written. |
| // A zero value for t means Write will not time out. |
| // Not all files support setting deadlines; see SetDeadline. |
| func (f *File) SetWriteDeadline(t time.Time) error { |
| return f.setWriteDeadline(t) |
| } |